Screening methods for the rapid determination of X or Y chromosomal ploidy (buccal smear Barr Body, blood smear Y flourescence analyses) will be applied to two subject populations: newborn males, and ambulatory adult males in a community. Lymphocyte karyotypes will be used to confirm the presence of gonosomal aneuploidy in individuals suspected thereof by screening test. The growth and development of proven aneuploid male neonates will be followed by means of observation, physical examination, developmental and psychological testing; and the educational and psychosocial achievement of proven aneuploid male adults will be assessed retrospectively. The aims of these procedures include the following: (1) to determine the absolute prevalence of gonosomal aneuploidy in these populations served by the Boston City Hospital; (2) in comparison with similar prevalence rates established for neonates at the Boston Hospital for Women (most of whom come from families of higher socioeconomic and educational levels), to determine whether the prevalence of gonosomal aneuploidy differs in the two major obstetrical facilities in Boston, and if so, the reasons for this difference; (3) to determine the characteristics of any syndrome associated with gonosomal aneuploidy, particularly with the prospective studies in neonates; and (4) also in comparison with similar observations in patients born at the Boston Hospital for Women, to determine whether the interaction of genotype with environment is important in determining the developmental patterns of gonosomal aneuploid individuals.